Pins in a series, low LE, continue to release, feature popular characters/genres, make pins desirable. They constantly bring in new collectors to the genre. Marquees, PTD's, paris PTN's, Beloved Tales, WDI Sorcerer Hats, etc all stay relevant, continue to add to the series.
Marquees are based in movies shown at the el Capitan. They have always had a premium over other DSF pins as they represent the soul purpose (pun intended) of DSF. Hollywood glitz and glamour in lights, the movies!! Then when marquees and the movie genre bang together, like say Tangled and Up, you have two very large collector groups going after a very limited number of pins. Those cross-genre blockbusters really create high demand and thus value.